Aberrations and distortion exist in every optical system. For optical systems with an exit pupil, such as near-to-eye display systems, aberrations across the pupil result in a “swimming” sensation of the image as the eye moves within the pupil to look at different objects displayed in various locations on a display screen. This is known as “pupil swim” and exists in all near-to-eye display systems. For example, in a head-mounted display (HMD) a user's eye occupies a region of space generally referred to as an eyebox (typically there is a respective eyebox for a left and a right eye of the user). The HMD displays and directs content to the eyeboxes. But as a user moves their eye within an eyebox and/or the position of the HMD changes relative to the position of the user's head, the location of the user's eye within an eyebox may change. Changes in the location of the eye within an eyebox may result in pupil swim, i.e., distortions in the content being presented to the user. Pupil swim can be problematic for HMDs for various reasons including, e.g., increased calibration difficulty, and motion sickness due to problems with vertical disparity.